New engine technologies, such as diesel engines with a common rail and a very high pressure fuel injection system, offer high performance but are very sensitive to fuel quality. There is therefore a benefit to using a fuel containing additives to improve its quality, such as additives to improve fuel distribution in the engine, additives to improve engine performance, and additives to improve engine operation stability. The quality of available commercial fuels does not always allow supplying the vehicle with fuel of good quality, even when enhanced with additives.
Furthermore, in order to meet new vehicle emission standards, especially for diesel, vehicles are progressively being equipped with Particulate Filters (PF). This is already the case in Europe, ever since the introduction of the Euro 5 standard. In most cases, a catalyst is used to help periodically burn the soot and thus regenerate the PF. It is no longer sufficient to efficiently regenerate the PF in order to stop the black smoke and soot. Now the major challenge is to reduce emissions of CO2 and nitrogen oxides NOx simultaneously while keeping the vehicle reliable, economical, and offering good performance, particularly when using biofuel. The vehicle must also be competitive against rival gas and hybrid offers. The use of a PF regeneration additive, carried by the fuel supplied to the engine (Fuel-Borne Catalyst—FBC), has been found to satisfy numerous criteria because it allows regenerating the PF more quickly and at a lower temperature than the competing technology known as Catalyst Soot Filter (CSF). Moreover, the FBC technology has no constraints concerning the ratio of NOx/soot, which is essential to integrating a catalyst that helps eliminates NOx, considering that the Euro 6 standard will take effect in 2014.
It is therefore advantageous to equip the vehicle with a device that allows introducing into the fuel an additive that helps regenerate the PF and/or fuel additives improving the fuel quality and/or the engine operation and/or the engine durability.
Known systems exist for introducing such additives into the fuel, such as FBC catalyst additives to assist with PF regeneration. These systems are generally based on a large reservoir, at least 2 to 3 liters in volume, to hold the supply of additive and which must be installed close to the fuel tank.
Current strategies for injecting doses of additive also rely on high precision dosing pumps, which must be controlled via an additional dedicated unit, the electronic control unit (or ECU). This dosing device must be managed closely to ensure there is sufficient additive in the fuel for good PF regeneration, but not too much so as to avoid premature PF clogging due to the mineral residues it collects from the PF regeneration. Conventionally, when the fuel level rises in the tank after adding fuel, the control unit indicates to the pump the amount of additive to be injected into the tank in order to maintain a constant concentration of additive in the fuel within the tank.
These dosing pumps are extremely precise and their cost is far from insignificant when considering the overall economics. Similarly, the ECU management of the system also plays a large role in the cost of the complete system.
The use of such a strategy also involves properly controlling the dosing system and verifying its state, which is particularly intrusive when managing vehicle failure modes.
In terms of maintenance, filling the reservoir is fairly difficult and is done through a connector adapted for the filling requirements and for the additive reservoir.
For example, diesel vehicles in the PSA group are equipped with such a device.
In certain geographical regions, such as the developing countries, it is difficult to guarantee that the reservoir will be properly filled throughout the life of the vehicle. It is therefore necessary to eliminate this uncertainty which can be detrimental to the automobile manufacturers image.
It is sometimes necessary to introduce additives into the fuel of motor vehicles which are intended to change the intrinsic qualities of the fuel or to act in the fuel distribution circuit or after combustion. These include, for example, anti-fungal agents, lubricant additives, detergent additives, antifreeze agents, or additives which help regenerate particulate filters, such as FBCs.
These additives can be added to the fuel when filling the fuel tank, dispensed in a diffuse and continuous manner into the fuel distribution circuit, or injected intermittently as a function of specific parameters such as, for example, fuel temperature, real-time or average fuel consumption, engine speed, or intervals of time.
Patent FR2668203 is already known, which discloses the introduction of a particulate filter regeneration additive into the fuel tank when filling the tank. This technical solution has the disadvantage of requiring an additive reservoir of significant volume as well as an electronic system for measuring the filling of the fuel tank. In addition, this technical solution increases the weight of the vehicle, and therefore its fuel consumption.
Also known are patents EP1061251 and U.S. Pat. No. 7,153,422, which disclose a fuel filter including an additive reservoir, where the additive is released into the fuel distribution circuit. This technical solution has the disadvantage of the additive being dissolved or diluted by the fuel introduced into the additive reservoir, which does not allow controlling the concentration of the additive released into the fuel.